Hybrid memory cell for spin-polarized electron current induced switching and writing/reading process using such memory cell

ABSTRACT

The present invention relates to a magnetoresistive hybrid memory cell comprising a first stacked structure comprising a magnetic tunnel junction including first and second magnetic regions stacked in a parallel, overlying relationship separated by a layer of non-magnetic material, wherein said first magnetic region being provided with a fixed first magnetic moment vector and said second magnetic region being provided with a free second magnetic moment vector which is free to be switched between the same and opposite directions with respect to said fixed first magnetic moment vector of said first magnetic region, a second stacked structure being at least partly arranged in a lateral relationship as to said first stacked structure and comprising a third magnetic region being provided with a fixed third magnetic moment vector and said second magnetic region; wherein said first and second structures being arranged in between at least two electrodes in electrical contact therewith. It further relates to a method of writing to and reading of a magnetoresistive hybrid memory cell, wherein a writing voltage pulse is applied to electrodes on both sides of only said second structure, and wherein a reading voltage pulse is applied to electrodes on both sides of only said first structure.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.11/024,945, filed Dec. 30, 2004, entitled “Hybrid Memory Cell forSpin-Polarized Electron Current Induced Switching and Writing/ReadingProcess Using Such Memory Cell” the entire contents of which are herebyincorporated by reference.

FIELD OF THE INVENTION

The present invention relates to non-volatile semiconductor memory chipsand more particularly to magnetoresistive memory cells adapted forspin-polarized electron current induced switching.

BACKGROUND

Magnetic (or magnetoresistive) random access memory (MRAM) is anon-volatile memory technology considered to be of great futureimportance as the standard memory technology for computing devices.

A schematic representation of a typical magnetoresistive memory cell isshown in FIG. 1. A magnetoresistive memory cell (also referred to as atunneling magneto-resistive or TMR-device) includes a structure havingferromagnetic layers 2, 4 respectively having a resultant magneticmoment vector 5, 6 separated by a non-magnetic layer (tunnel barrier) 3and arranged into a magnetic tunnel junction (MTJ) 1. Digitalinformation is stored and represented in the magnetic memory cell asdirections of magnetic moment vectors in the ferromagnetic layers. Morespecifically, the resultant magnetic moment vector 6 of oneferromagnetic layer 4 is magnetically fixed or pinned (typically alsoreferred to as the “reference layer”, “pinned layer” or “fixed layer”),while the resultant magnetic moment vector 5 of the other ferromagneticlayer 2 (typically also referred to as the “free layer”) is free to beswitched between two preferred directions, i.e., the same and oppositedirections with respect to the fixed magnetization 6 of the referencelayer 4. The orientations of the magnetic moment vector 5 of the freelayer 2 are also known as “parallel” and “antiparallel” states,respectively, wherein a parallel state refers to the same magneticalignment of the free and reference layers (upper diagram of FIG. 1),while an antiparallel state refers to opposing alignments therebetween(lower diagram of FIG. 1). Accordingly, a logic state of amagnetoresistive memory cell is not maintained by power as in DRAMs, butrather by the direction of the magnetic moment vector of the free layerwith respect to the direction of the magnetic moment vector of thereference layer (for instance, a logic “0” in the case of a parallelalignment of magnetic moment vectors and a logic “1” in the case of anantiparallel alignment therebetween).

Depending upon the magnetic states of the free layer, the magneticmemory cell exhibits two different resistance values in response to avoltage applied across the magnetic tunnel junction barrier, wherein theresistance is “low” when the magnetization is parallel and “high” whenthe magnetization is antiparallel, so that a detection of changes inresistance allows an MRAM-device to provide logic information stored inthe magnetic memory element.

A magnetic memory cell typically is written to through the applicationof magnetic fields from bi- or uni-directional currents. For writing ofmagnetic memory cells different writing (switching) scenarios are knowndepending on the actual configuration of the magnetoresistive memorycell such as Stoner-Wohlfahrt-switching or adiabatic rotationalswitching (toggle-switching) which are well-known to those skilled inthe art and therefore need not be further detailed here.

To be useful in present day electronic devices, such as digital camerasor the like, very high density arrays of magnetic memory cells must beused, thus rendering a scaling-down of MRAM cells one of the mostimportant issues, which, however, requires several problems to besolved.

Down-scaling of MRAM cells requires smaller and smaller magnetic tunneljunctions, which proves problematic, since for a given aspect ratio andfree layer thickness, the activation energy, being dependent on the freelayer volume, scales down like w, where w is the width of the magneticcell. Otherwise, in down-scaling, the switching fields increase roughlylike 1/√{square root over (w)}, so that magnetic field selectedswitching becomes ever harder, but at the same time the magnetic cellsloose their information more and more rapidly due to thermal activation.A major problem with having a small activation energy (energy barrier)is that it becomes extremely difficult to selectively switch one MRAMcell in an array, where selectability is seen to allow switching withoutinadvertently switching other MRAM cells. The memory cells thereforestill need to retain a sizeable shape or induced anisotropy in order tomaintain thermal stability.

Reference is now made to FIG. 2 showing a diagram in which the energybarrier height ΔE for switching of magnetic moment vector 5 of magneticfree layer 2 of rectangular MTJ 1 of FIG. 1 having lateral dimensions Lfor length and l for width (see insert) and a low thickness of about 2nm is plotted against its width l. It is further assumed thatmagnetization of the magnetic free layer 2 is aligned along directions±x. Considering a simple Arrhenius law with a 0.1 nsec characteristicattempt time, requesting a ten years stability is equivalent to settingthe barrier height between stable states (−x and −x) at about 45 k_(B)T(T=300° K., room temperature, k_(B) is Boltzmann constant).

As can be seen from FIG. 2, an aspect ratio L/l=2 proves sufficient forovercoming the energy barrier height lower limit criterion if l remainsgreater than about 60 nm. A slight increase of the aspect ratio pushesthe limit further out. It also becomes clear that as sizes shrink down,the superparamagnetic limit becomes closer and closer.

Another problem in scaling down magnetoresistive memory cells may beseen in that in the case of magnetic field selected switching of memorycells the cell sizes need to be smaller than sizes of the current linesfor generating of magnetic fields in order to ensure essentiallyhomogeneous magnetic fields over the whole memory cell area.

In an attempt to overcome the above problems, a new concept of writingto magnetoresistive memory cells has been recently proposed, where thereversal of the magnetic moment vector of the magnetic free layer isgenerated not by external magnetic fields but by spin-polarizedelectrons passing perpendicularly through the stack of memory celllayers. For a detailed description of that concept, see for instanceseminal U.S. Pat. No. 5,695,864 to Slonczewski and U.S. Pat. No.6,532,164 to Redon et al., the disclosures of which are incorporatedherein by reference.

In the above new concept, by sending an electric current through amagnetic layer having a particular magnetization, spins of electrons areoriented by quantum-mechanical magnetic exchange interaction with theresult that the current electrons leave the magnetic layer with apolarized spin. Alternatively, where spin-polarized electrons are passedthrough a magnetic layer having a particular magnetic moment vector in apreferred easy axis direction, these spin-polarized electrons will causea continuous rotation of the magnetic moment vector which may result ina reversal of the magnetic moment vector along its easy axis. Hence,switching of the magnetic moment vector between its two preferreddirections along the easy axis may be effected by passing spin-polarizedelectrons perpendicularly through the magnetic layer.

Recent experimental data (see S. I. Kiselev et al., Nature 425 (2003),380 and W. H. Rippard et al., Phys. Rev. Lett. 92 (2004) 027201) confirmthe very essence of magnetic moment transfer as a source of magneticexcitations and, subsequently, switching. These experiments confirmtheoretical predictions (see J. C. Sloncezwski, J. Magn. Magn. Mater.159 (1996) L1 and M. D. Stiles & A. Zangwill, Phys. Rev. B66, (2002)014407) stating that the leading torque term acting on the magnetizationunder conditions of spin-polarized DC current is proportional to:$\frac{\mathbb{d}m}{\mathbb{d}t} \propto {P\left\lbrack {m \times \left( {m \times p} \right)} \right\rbrack}$where m, p and P are the magnetization direction in space, thepolarization direction of the electron current (density per unit area J)and a polarization function, respectively. A direct inspection of aboveequation indicates that the torque will be maximum when p is orthogonalto m.

Reference is now made to FIGS. 3A and 3B, where a schematicrepresentation of both a magnetic free layer 2 and a magnetic layer 7for spin-polarizing of current electrons in a stacked arrangement isshown. In that configuration, the magnetic free layer 2 is provided witha magnetization easy axis where a magnetic moment vector 5 is free to beswitched between two preferred directions thereof. Magnetic layer 7 isprovided with a fixed magnetic moment vector 8 being perpendicular tothe magnetic moment vector 5 in the configuration of FIGS. 3A and 3B.FIG. 3A illustrates a case where a current density J of an electroncurrent (not illustrated) flowing perpendicularly through the layers isassumed to be nil, while in FIG. 3B the current density J is assumed tobe different from zero. Accordingly, on the one hand, in FIG. 3A whereno current is passing through the layers, magnetic moment vector 5remains unchanged, while, on the other hand, in FIG. 3B, electronspassing through the layers are spin-polarized when flowing throughmagnetic layer 7 by the effect of magnetic exchange interaction. If apolarization direction p of the current electrons belongs to the planeof the magnetic free layer 2, then rotation of the magnetic momentvector 5 occurs in the plane of magnetic free layer 2 and the torquebecomes nil when m becomes parallel to p (that case is not shown inFIGS. 1A, 1B). Alternatively, if p is perpendicular to the plane of themagnetic free layer 2 (case shown in FIGS. 1A, 1B), then the initialtorque pulls the magnetic moment vector 5 out of its plane, thuscreating a demagnetizing field H_(D) perpendicular to the magnetic freelayer 2 plane, with the result that a precession movement of themagnetic moment vector 5 around the demagnetizing field H_(D) may nowtake place.

In other words, in a magnetic element such as the soft element of anMRAM cell, the magnetization direction though not far from being uniformfails to be so as a result of demagnetizing effects. Coherence duringmagnetic switching may nevertheless be preserved if the field exerting atorque on the magnetization is perpendicular to the soft layer. In orderto achieve this, the best strategy is to apply a magnetic field normalto the mean magnetization direction within the soft element and in theplane of the layer. The initial torque γ₀[m×H_(a)], where γ₀, m, H_(a)are a gyromagnetic ratio, magnetization vector and applied magneticfield, respectively, pulls the magnetization out of the plane leading tothe growth of a demagnetizing field that remains essentially normal tothe plane of the layer. The magnetization may now precess around thedemagnetizing field under the torque γ₀[m×H_(D)], where H_(D) is thedemagnetizing field.

In order to observe precessional switching, three conditions have to befulfilled, namely, both the rise and fall times of the field pulse needto be “short” and the length of the pulse has to be tailored veryaccurately, where “short” means a time small when compared to timerequested for the magnetization to make half a turn. Let T and f be theperiod and precession frequency, respectively. A half a turn rotationmeans a time equal to T/2. One has T=1/f and f depends on the amplitudeof the demagnetizing field: ω=2Πf=γ₀H_(d). On the other hand, thedemagnetizing field scales with the angle of the magnetization out ofthe sample plane.

An example may illustrate this: suppose the magnetization leaves itsplane by an angle of

=10°, then the demagnetizing field amplitude will amount to aboutH_(d)≈M_(s) sin(10°). For a typical soft material with saturationinduction μ₀M_(s)=1 Tesla, this means a precession frequency equal tof=(ω/2Π)=γ₀M_(s) sin(10°)≈5 GHz. The period then amounts to 200picoseconds, and the time necessary for a half turn rotation wouldtypically be T/2=100×10⁻¹² sec (100 picoseconds (ps)). In summary, owingto values chosen in the sample, the pulse length should be close to 100ps and the fall and rise times much shorter than 100 ps. Laboratoryrealizations allow for pulse rise and fall times of the order of 20 ps.

Precessional switching is a very robust and fundamental effect. In alarge scale memory, however, due to various sources of impedance, it isexpected that maintaining such an accuracy in the definition of thefield pulses might prove extremely problematic.

In order to result in a desired reversal of the free magnetic momentvector, precession movement has to be controlled appropriately, which,however, has not been demonstrated in prior art.

SUMMARY

In light of the above, the invention provides a magnetoresistive memorycell allowing a further cell size down-scale without causing severeproblems as to an increase of switching-fields and decrease ofactivation energy.

The invention further provides a method of writing to (switching) andreading of resistance states of above magnetoresistive memory cells.

According to a first aspect of the invention, a magnetoresistive hybridmemory cell comprises a first stacked structure being provided with amagnetic tunnel junction including first and second magnetic regionswhich are stacked in a parallel, overlying relationship and areseparated by a layer of non-magnetic material. The first magnetic regionis provided with a fixed first magnetic moment vector, while the secondmagnetic region is provided with a free second magnetic moment vectorwhich is free to be switched between the same and opposite directionswith respect to above fixed first magnetic moment vector of the firstmagnetic region. The magnetoresistive hybrid memory cell furthercomprises a second stacked structure which at least partly is arrangedin a lateral relationship as to the first stacked structure andcomprises both a third magnetic region and the second magnetic region,the latter one thus being a common magnetic region of both first andsecond stacked structures. The third magnetic region is provided with afixed third magnetic moment vector, which typically and preferably isaligned in an orthogonal direction as to the free second magnetic momentvector of the second magnetic region. Furthermore, the first and secondstructures are arranged in between at least two electrodes in electricalcontact therewith.

Magnetic anisotropy of the second magnetic region may be due to shapeanisotropy and/or intrinsic anisotropy. In the former case, the secondmagnetic region may, for instance, be elliptic in shape.

In a particularly preferred embodiment of the first aspect of theinvention, one of above-cited electrodes for contacting the first andsecond structures being arranged on one side of the first and secondstructures is a common electrode in electrical contact with both firstand second stacked structure. Such common electrode is preferablypositioned adjacent the second magnetic region, in particular in directelectrical contact therewith.

In another particularly preferred embodiment which preferably may becombined with a common electrode connecting the first and secondstructures on the one side, separate electrodes for each one of thefirst and second structures are provided on the other side of the firstand second structures. Such particular design allows for an advantageousdecoupling of write and read functions, which, hence, can be optimizedindependently.

Alternatively, it is also possible to envisage separate electrodes foreach one of the first and second structures which are provided on bothsides of them.

According to a second aspect of the invention, a method of writing toand reading of a magnetoresistive hybrid memory cell is given, whichcomprises the following steps: providing of a magnetoresistive hybridmemory cell as above-described with regard to the first aspect of theinvention; applying of a writing voltage pulse to electrodes on bothsides of only the second structure (and not the first structure)resulting in a current pulse flowing through the second magnetic regionfor writing of the free second magnetic moment vector; applying of areading voltage pulse to electrodes on both sides of only the firststructure (and not the second structure) resulting in a current pulseflowing through the magnetic tunnel junction. Accordingly, applyingwriting and reading voltage pulses to second and first stackedstructures, respectively, allows for an advantageous decoupling ofwriting and reading functions.

In a mostly preferred embodiment of the second aspect of the invention,a switching voltage pulse is applied which is adapted to result in acoherent rotation over half a full turn of the free second magneticmoment vector in total. Such coherent rotation over half a full turn ofthe free second magnetic moment vector may preferably be achieved inapplying writing voltage pulses having a slow rise time and a fast falltime. The terms “slow” and “fast”, here, have a meaning exactlyanalogous to the precessional switching case described in theintroductory portion, that is, “fast” means times shorter than a halfprecession cycle, while “slow” means times substantially larger than afull precession cycle. Hence, precessional switching requires both“fast” field pulse rise and fall times, whereas spin injection in thepresent geometry requires “slow” current rise times. This is a result ofextended numerical simulation work done by the inventors. A “fast”current rise time would lead to a lot of unwanted magnetization“ringing” (response oscillations).

As also explained in the introductory portion with respect to theprecessional switching case, “coherent rotation” means that,irrespective of the magnetization distribution (not a perfectly uniformdistribution), the torque acts in such a way that all moments aresubjected to a torque acting in the same direction, thus maintainingcoherence of the distribution. This is not at all the case for theconventional spin injection cells for which by different simulationsmarkedly chaotic behaviors have been predicted. Other and furtherobjects, features and advantages of the invention will appear more fullyfrom the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate presently preferred embodiments ofthe invention, and together with the general description given above andthe detailed description given below, serve to explain the principles ofthe invention.

FIG. 1 is an exemplary schematic representation of a typical magnetictunnel junction included in an MRAM cell;

FIG. 2 shows a diagram illustrating energy barrier height for switchingof an MRAM cell versus width dimension 1;

FIGS. 3A and 3B illustrate a stacked structure comprised of a magneticlayer having fixed magnetization and a magnetic free layer having a freemagnetization free to be rotated with respect to the fixed magnetizationdue to spin-polarized electron current flowing therethrough;

FIG. 4 is a schematic representation of an embodiment of a hybridmagnetoresistive memory cell of the invention;

FIG. 5 shows a diagram illustrating writing current I and processionangle Φ in the single spin limit versus time;

FIGS. 6A and 6B show a typical writing current pulse having slow riseand fast decay times resulting in a typical sawtooth profile (FIG. 6A)and curve illustrating writing current versus pulse length resulting insingle reversal events; and

FIGS. 7A and 7B show diagrams analogous to that one FIGS. 6A and 6B inthe case of a limitation to the half of the platelet area.

DETAILED DESCRIPTION

Embodiments of the present invention will be described in detail belowwith reference to the accompanying drawings. Referring to FIG. 4, anembodiment of the hybrid memory cell of the invention is explained.Based on a conventional magnetic memory cell, the hybrid magnetic memorycell of the invention comprises a first stacked structure 9 beingcomprised of a magnetic tunnel junction (MTJ) which includes a fixedfirst magnetic region 10 and a free second magnetic region 11 stacked inparallel, overlying relationship and separated by a layer 12 tunnelingbarrier. Magnetic free region 11 is made of a magnetic material such asCoFe/NiFe and is provided with a free second magnetic moment vector 18free to be switched between oppositely aligned orientations along itsmagnetic easy axis. Magnetic reference region 10 is comprised of twolayers 13, 14 of ferromagnetic materials such as CoFe with itsmagnetizations being antiferromagnetically coupled resulting in a fixedfirst magnetic moment vector 17. Intermediate layer 12 is made of anonmagnetic material such as AlO_(x). The hybrid memory cell of theinvention further comprises a second stacked structure 23 which iscomprised of the free second magnetic region 11, a third magnetic region20 being provided with a fixed third magnetic moment vector 21 which isperpendicularly directed to the second magnetic moment vector 18, aconductive layer 24 for instance made of Au and being arranged on top ofthird magnetic region 21 in contact therewith, and a further conductivelayer 19 for instance made of Cu and being arranged beneath thirdmagnetic region 21 in contact therewith. Above second magnetic region11, first and second stacked structures 9 and 23, respectively, arearranged in a lateral relationship leaving an intermediate gap G betweenthem. Further, first and second stacked structures are arranged betweena common bottom electrode 16 connecting both first and second structuresand separate top electrodes 15, 16, that is to say a separate topelectrode for each one of stacked structures.

Having separate top electrodes 15, 22 for each one of both first andsecond stacked structures, hybrid magnetoresistive memory cell of FIG. 4enables a favorite decoupling of write and read functions.

Further characteristics of the invention are now explained:

Let call F the minimum feature size (smallest dimension) of thetechnology used, e.g. 0,11 μm, 90 nm, 65 nm following the semiconductorroadmap. A magnetic memory cell today may hardly be smaller than 2 F²due to the necessity for maintaining some kind of shape anisotropy(toggle switching, however, allows for circular elements). As mentionedabove within the context of field addressing, the field necessary tocommute cells grows with decreasing cell size. On the contrary, thesmaller the active region of spin-injection, the smaller the detrimentaleffect due to the field created by the requested current density (theso-called Oersted field). It is common knowledge that, for usual 3dferromagnetic materials, spin-injection ceases to be relevant for cellsizes exceeding some 100 nm.

In the proposed scheme, the minimal cell size is 3 F². It means thatdistance G in FIG. 4 may not be smaller than F due to processingconstraints. On the other hand, allowing for a 1 F² area for thespin-injection region (the right part of FIG. 4) is extremely favorablebecause it complies with the necessity to decrease as much as possiblethe Oersted field. The present scheme mimics through spin-injection aprecessional type motion of the magnetization in the spin-injectionregion. It is a fundamental process due to the relative orientations ofthe magnetization 21 in layer 20 and magnetization 18 in layer 11.

Now, once the magnetization 18 in layer 11 has been reversed under layer20, a wall is created, which has inertia, so that once it is set intomotion, it will keep-up moving for some time that is mainly controlledby the damping in the material. As simulations by the inventors haveshown, this “wall launching” mechanism allows for wall motion throughout the extent of the cell layer 11. Additionally, some current flowingfrom layer 22 into sublayer 16 will also flow along the full length ofthe cell layer 11. Because flowing in a ferromagnetic material, such acurrent is spin-polarized and exerts a pressure on the wall, thusassisting wall motion. This last effect, is however, hard to quantifybecause it depends crucially on the difference in electrical resistivitybetween layers 11 and 16. This last effect has been neglected by thesimulations made by the inventors.

Using cell design for spin injection suffers from the drawback ofneeding to simultaneously optimize both the writing current and the readsignal. Giant magnetoresistance structures would exhibit weak readsignals. Moreover, the signal decreases with decreasing cell size.Tunnel junctions do not suffer from this basic drawback, but themechanisms that eventually allow cell switching through very shallowtunnel junctions remain unclear. Shallow tunnel junctions result insmaller read signals. From an engineering point of view, the larger theread signal, the better.

In the proposed scheme, thermal stability is improved through thegeometry: a 3 F² cell size remains thermally stable on the long term forthe smallest F dimensions because of the aspect ratio as shown in FIG. 2(F is 1 in FIG. 2). It may be added that the magnetostatic couplingbetween layer 20 with magnetization 21 and layer 11 with magnetization18 will contribute to an increased thermal stability.

As above stated, in the proposed scheme, write and read functions mayindependently optimized, where optimization means here both optimizationof the read signal (state of the art tunnel junction 9 in the lowcurrent regime, and, best couple of materials between layers 11 and 13,and optimization of the write current (optimized spin-polarizationthrough the choice of materials in layers 11 and 20, and, optimizedspin-accumulation through a proper choice of the thicknesses of layers21, 20 and 19.

Now referring to FIGS. 5 through 7, a numeric simulation concerning themethod of writing to a magnetoresistive hybrid memory cell is explained.

As can be seen from FIG. 5, a numeric simulation in the single spinlimit reveals that controlled precession of the free second magneticmoment vector may be achieved through the application of current pulseswith a slow rise time and a fast fall time.

Further characteristics of FIG. 5 are given: FIG. 5 (single spin typesimulations) shows that, for asymmetrical current pulses, a properchoice of the current density allows for a controlled magnetizationrotation. Φ (in °) to the right of the figure is seen to move in stepsof 180°, meaning one half a turn, a full turn, three half-a-turn etc.The figure applies to the case of FIG. 3B, not to FIG. 4. It was a firststep in order to explain that control was solely possible if allowingfor pulse asymmetry.

An extension of such calculations to the micromagnetic regime confirmsthis prediction as can be seen from FIGS. 6A and 6B. Current injectionthrough half of the platelet area yields the following results, whichare given in FIGS. 7A and 7B.

FIGS. 6B and 7B are computed operational margins as determined by fullmicromagnetic simulations (meaning that now the detailed aspects of themagnetization distribution both in space and time are taken intoaccount) in a parameter space where the horizontal scale is the pulselength as defined in FIGS. 6A and 7A, respectively, and the verticalscale the current density at the end of the pulse.

FIG. 6 concern current densities that are homogeneous through the entirecell. FIG. 6 are therefore not directly usable for the presentinvention. On the contrary, FIG. 7 apply to cells where the currentflows in only half of a 2 F² cell, i.e. a cell, where distance G in FIG.4 would be ideally zero. FIG. 7 show that a fairly sizeable operationalmargin may be expected with pulse durations in the 0.15 to 0.45 ns (150to 450 ps) and maximum current densities in 0.4 to close to 0.475 A/μm².Constraints on pulse durations are expected to be rather weak. Currentdensities are more challenging as the margin does not exceed some 15%,according to extended and state of the art numerical simulations.

Obviously many modifications and variations of the present invention arepossible in light of the above description. It is therefore to beunderstood, that within the scope of appended claims, the invention maybe practiced otherwise than as specifically devised.

While the invention has been described in detail and with reference tospecific embodiments thereof, it will be apparent to one skilled in theart that various changes and modifications can be made therein withoutdeparting from the spirit and scope thereof. Accordingly, it is intendedthat the present invention covers the modifications and variations ofthis invention provided they come within the scope of the appendedclaims and their equivalents.

REFERENCE LIST

-   1 Magnetic tunnel junction-   2 Ferromagnetic layer-   3 Tunnel barrier layer-   4 Ferromagnetic layer-   5 Magnetic moment vector-   6 Magnetic moment vector-   7 Ferromagnetic layer-   8 Magnetic moment vector-   9 First stacked structure-   10 Fixed first magnetic region-   11 Free second magnetic region-   12 Tunnel barrier layer-   13 Ferromagnetic layer-   14 Ferromagnetic layer-   15 Top electrode-   16 Common bottom electrode-   17 Fixed first magnetic moment vector-   18 Free second magnetic moment vector-   19 Conductive layer-   20 Third magnetic region-   21 Fixed third magnetic moment vector-   22 Top electrode-   23 Second stacked structure-   24 Conductive layer

1. A method of writing to and reading of a magnetoresistive hybridmemory cell, comprising the following steps: providing of amagnetoresistive hybrid memory cell comprising: a first stackedstructure comprising a magnetic tunnel junction including first andsecond magnetic regions stacked in a parallel, overlying relationshipseparated by a layer of non-magnetic material, wherein said firstmagnetic region being provided with a fixed first magnetic moment vectorand said second magnetic region being provided with a second freemagnetic moment vector which is free to be switched between the same andopposite directions with respect to said fixed first magnetic momentvector of said first magnetic region; a second stacked structure beingarranged in a lateral relationship to said first stacked structure andcomprising a third magnetic region being provided with a fixed thirdmagnetic moment vector and said second magnetic region; wherein saidfirst and second structures being arranged in between at least twoelectrodes in electrical contact therewith; applying of a writingvoltage pulse resulting in a writing current pulse flowing trough saidsecond magnetic region for switching of its free magnetic moment vectorto electrodes on both sides of only said second structure; applying of areading voltage pulse resulting in a reading current pulse flowingthrough said magnetic tunnel junction to electrodes on both sides ofonly said first structure.
 2. The method of switching a magnetoresistivehybrid memory cell as claimed in claim 7, wherein said writing voltagepulse is applied adapted to result in a coherent rotation over half afull turn in total.
 3. A method of writing to and reading of amagnetoresistive hybrid memory cell, comprising the following steps:providing of a magnetoresistive hybrid memory cell comprising: a firststacked structure comprising a magnetic tunnel junction including firstand second magnetic regions stacked in a parallel, overlyingrelationship separated by a layer of non-magnetic material, wherein saidfirst magnetic region being provided with a fixed first magnetic momentvector and said second magnetic region being provided with a second freemagnetic moment vector which is free to be switched between the same andopposite directions with respect to said fixed first magnetic momentvector of said first magnetic region; a second stacked structure beingat least partly arranged in a lateral relationship to said first stackedstructure and comprising a third magnetic region being provided with afixed third magnetic moment vector and said second magnetic region;wherein said first and second structures being arranged in between atleast two electrodes in electrical contact therewith; applying of awriting voltage pulse resulting in a writing current pulse flowingtrough said second magnetic region for switching of its free magneticmoment vector to electrodes on both sides of only said second structure,wherein said switching voltage pulse is applied adapted to result in acoherent rotation over half a full turn in total having a slow rise timeand a fast fall time; applying of a reading voltage pulse resulting in areading current pulse flowing through said magnetic tunnel junction toelectrodes on both sides of only said first structure.
 4. The method asclaimed in claim 7, wherein said fixed magnetic moment vector of saidthird magnetic region being perpendicularly aligned to said freemagnetic moment vector of said second magnetic region.
 5. The method asclaimed in claim 7, wherein one of said electrodes arranged on one sideof said first and second structures is a common electrode connectingsaid first and second structures.
 6. The method as claimed in claim 11,wherein said common electrode is positioned adjacent said secondmagnetic region.
 7. The method as claimed in claim 12, wherein separateelectrodes for each one of said first and second structures are providedon the other side of said first and second structures.
 8. Themagnetoresistive hybrid memory cell as claimed in claim 7, whereinseparate electrodes for each one of said first and second structures areprovided on both sides of said first and second structures.